Hydraulic power transmission with flow control by-pass valve



Aug. 17, 1948. J, J, GEORGE 2,447,406

HYDRAULIC POWER TRANSMISSION WITH FLOW CONTROL BYPAss VALVE Filed Dec. 26, 1944 Patented Aug. 17, 1948 HYDRAULIC POWER TRANSMISSION WITH FLOW CONTROL BY-PASS VALVE;

Joseph J. George, Wyandotte, Mich., assignor to Vickers Incorporated, Detroit, Mich., a. corporation of Michigan Application December 26, 1944, Serial No. 569,828

Claims. 1

This invention relates to power transmissions, particularly to those of the type comprising two or more uid pressure energy translating devices, cne of which may function as a pump and another as a uid motor.

The invention is particularly adapted for use with a reeling device and has been illustrated as applied to a mechanism of this character although it will be understood that the invention is equally adaptable to other applications.

In reeling devices wherein a strip of material is wound upon a reel in successive layers, the diameter of the reeled material progressively increases as the material is wound on the reel. If the material is fed to the reel at a constant speed, the speed of the ree1 must be decreased as the diameter of the reeled material increases, and, likewise, if a constant tension is maintained on the material being reeled, a progressively increasing torque must be applied to the reel as the reel diameter increases. As the diameter of the wound material increases, the torque of the driving motor must gradually increase, and the speed of the motor must gradually decrease. The reason for this is that the strip of material is being delivered at a uniform linear speed while the ree1 increases in diameter, and its rotary speed decreases relative to the peripheral speed.

'In the past, hydraulic power transmissions comprising a xed displacement pump and a variable displacement motor, the displacement of which was controlled by an automatic pressure responsive regulator, have been used fairly satisfactorily to maintain constant tension on the material being reeled. In other cases, a transmission utilizing a fixed displacement pump and motor together with a throttle valve bleed-01T to control the speed of the motor has been used with partial success. The first method of maintaining constant tension on a material being Wound on the ree1 is more expensive than the second method because of the difference in cost between a constant and a variable displacement motor. The second method, although less expensive, was not as accurate because of the fact that the throttle valve bleed-off requires'manual operation and control, and slight errors in judgment sometimes lead to serious consequences.

It is an object of the present invention to provide a flow regulating device for a hydraulic power transmission containing preferably a fixed displacement type pump and motor driving a reel, but which may contain variable types, which will automatically vary the output speed of the transmission causing an increase in torque and a de- 2 crease in speed of the driving motor as the diameter of the material being Wound on the reel increases.

It is also an object of the present invention to provide a flow regulating device for use in a hydraulic power transmission, as above mentioned, which will operate to maintain constant tension upon the material being reeled and Which is operable over a wide range of speeds and reel diameters and which avoids the use of mechanism in contact with or associated with the ree1 or the strip material to determine the tension.

It is a further object of this invention to provide a pressure responsive, iiow regulating device for a hydraulic transmission for driving a reel or other load device, 4containing a fluid pump and motor, which is responsive directly to pressure developed in the transmission fluid and which will automatically change the speed of the motor driving the reel or other load device in response to changes in torque.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing: the single figure shown is a diagrammatic view of a power transmission system incorporating a preferred form of the present invention.

Referring now to the single figure, there is illustrated a pump I0 which may be driven by an electric motor I2, the pump I0 having a. suction conduit I4 for withdrawing fluid from a tank I0 and a pump delivery conduit I8 connected to an inlet port 20 of a flow regulating device 22 which also has an outlet port 24, an exhaust port 28, a drain port 21, and a. control port 29.

Direct application of fluid from pump I0 to a fluid motor 28, used for the purpose of driving a reel 30 upon which a strip of material will 4be wound, is by means of a .suitable manually-operated control valve 32. Conduits 34 and 36 connect valve 32 with motor 28, and conduits 38 and 40, respectively, connect ow regulating valve 22 with control valve 32 and control valve 32 with tank I6.

Valve 32 is a means of stopping and starting motor 28. In one position, valve 32 will start motor 28 by connecting conduits 34 and 3B and directing fluid under pressure from pump I0 to motor 28 and at the same time connecting conduits 38 and 40 so as to direct the return iiow of uid from motor 28 to tank I6. In another position, control valve 32 will connect conduits 3l and 40, blocking connection between conduits 34 and 36 so as to direct the full flow of nuid from pump I totnk I6, unloading pump |0 completely and thus stopping motor 28.

Flow regulating valve 22 is comprised of a motor pressure responsive throttle 42 consisting of a piston 44 connected to which is a stem 46 which is tapered at its end to form a metering valve 48. The valve 42 is shiftable within a longitudinal stepped bore 50 formed within valve 22. A spring 52 of predetermined resistance abutting the underside of piston 44 originally positions piston 44 so that an upper chamber -54 between the upper side of piston 44 and the inner side of an end cap 56 is formed within bore 50. A lower chamber 58 is also formed on the underside of piston 44 within bore 50.

Within another longitudinal stepped bore 60 of valve 22 is a compensating valve 62 comprising a piston 64 connected to which is a stem 66 tapered at its end to form an overilow valve 68 to rest on a seat formed within valve 22. The valve 62 has a guide 12 connected to the upper side of piston 64 shiftable Within the bore 60. The valve 62 when positioned in bore 60 forms an upper chamber 14 on the upper side of piston 64 and a lower chamber 16 on the underside of piston 64. A spring 18 located in upper chamber 14 and abutting the upper side of piston 84 biases valve 88 to the closed position.

A branch conduit 80 connects conduit 38 with control port 28 of valve 22. The letter contains a restriction at 82. A passageway 84 connects control port 29 with chamber 54 of valve 42 and also chamber 14 of valve 62. Another passageway 86 connects the upper chamber 14 of valve 62 with a valve 88 consisting of a ball valve 80 in back of which is a spring 82 of predetermined resistance which biases valve 80 to the closed position to rest on a seat 93, the original setting of spring 8-2 being determined by an adjustable screw 84 over which is threaded a protective cap 95. An exhaust passageway 86 connects valve 88 with an exhaust chamber 98 which also serves as an overflow chamber for valve 62. Exhaust chamber 98 is in open. communication with tank I8 by means of exhaust port 26 and a conduit |00 which connects tank I6 with exhaust port 26.

A passageway |02 connects chamber 16 of valve 62 with the outlet port 24 oi.' valve 22.

Valve 48 is originally positioned in passageway |02 by means of an adjustable screw |04, one end of which abuts the upper side of piston 44. Adjustable screw |04 is threaded through end cap 56 and has threaded over it a protective cap |06. Valve 48` is prevented from completely blocking passageway |02 by means of a set screw |08 over which is threaded a protective cap ||0. Any seepage of uid past piston 44 to chamber 58 is drained by means of a passageway I2 connecting chamber 58 with drain port 21 and a conduit |I4 connecting drain port 21 with tank I6.

In operation, with the pump I0 running and with the valve 32 shifted to direct fluid from pump |0 to motor 28 and from motor 28 back to tank I8, uid under pressure from pump I0 is directed by conduit |8 to inlet port 20 of valve 22. The iluid under pressure then enters chamber 16 of valve 62, passageway |02, valve 48, outlet port 24, conduit 38, valve 32, and conduit 34 to motor 28. Fluid from motor 28 is directed back to tank I6 by means of conduit 36, valve 32 and conduit 40. As the material is just starting to be wound upon reel 30, the tension upon the winding material is at normal operating value. Fluid pressure in conduits |8, 38 and 34 is low because the radius at which the strip tension is acting is small, creating a low torque, and the fluid motor is operating the reel at the highest possible speed, its displacement being such as to cause the peripheral speed of the reel to be of the same value as the speed of the winding strip of material.

Fluid under pressure from pump l0 entering chamber 16 acts on the underside of piston 64 of valve 62 and, because valve 68 is seated which prevents fluid from being bypassed to tank I8 through exhaust chamber 98 and conduit |00, is conducted through passageway |02 out of port 24, conduit 38, and branch conduit to the motor port 28 of valve 22. By means of passage- Way 84, fluid under pressure equivalent to pressure at motor 28 is conducted to chamber 54 of valve 42, acting on the upper side of piston 44 against resistance oil'ered by spring 52, and to chamber 14 of valve 62, acting against the upper side of piston 64, and by passageway 86 to valve 88 against the resistance offered by spring 82. As the total eifective area of piston 64 is the same in chamber T6 as it is in chamber 14, the total pressure drop across throttle 42 will have to be greater than the resistance of spring 18 before valve 68 will lift from its seat 10.

The purpose of valve 62 is to maintain a constant uniform pressure drop across throttle 42 for every given position of the throttle. If the pressure drop across throttle 42 is at any time greater than the setting of spring 18, valve 68 will lift from its seat 10 and allow enough fluid to escape to exhaust chamber 88 of valve 22 and from chamber 98 to tank I6 by means of exhaust port 26 and conduit |00 to maintain constant the pressure drop across throttle 42.

Valve 42 acts as a metering device to meter a maximum ow of uid under pressure from pump |0 to motor 28 when the diameter of the winding material on reel 30 is at its smallest and to gradually decrease the supply of uid to motor 28 as the diameter of the winding material on reel 30 increases. Spring 52 of valve 42 originally positions valve 48 in passageway |02 so that valve 48 permits a maximum flow of iluid from pump |0 through passageway |02 from chamber 15 of valve 62 to outlet port 24 of valve 22 when the strip of material is just beginning to be wound upon reel 30. Valve 48 will gradually close passageway |02 in response to an increase of pressure at motor 28.

As the winding strip of material increases in diameter on reel 30 causing an increase of torque at motor 28 which causes an increase of pressure at motor 28, the increase of pressure acts on the upper side of piston 44 tending to close valve 48. As valve 48 gradually closes down, there will be an increase of pressure in chamber 16 of valvey 62 acting on the underside of piston 64, thereby lifting valve 88 and letting enough uid escape through seat 10, exhaust chamber 88, exhaust port 26 and conduit |00 to tank I6 to maintain constant the pressure drop across throttle 42. Pressure ahead of the throttle 48 acts on the bottom of piston 64, while pressure beyond the throttle acts on the top thereof, being transmitted through conduits 80 and 84 and restriction 82. Thus, when either pressure tends to rise in relation to the other, it will upset the balance of forces on piston 64, causing it to shift and counteract such pressure change by adjusting the quantity of fluid being bypassed to tank through valve seat 10. Thus, as the dicercasi ameter of the winding material on reel 30 increasesL causing an increase of pressure in conduitsf18, 38 and 34, throttle 42 and overflow valve 62 are responsive to this increase of pressure, and the amount of fluid under pressure going to motor 28 gradually decreases with an increase oi pressure at said motor, thereby decreasing the speed of the motor and maintaining a constant uniform tension on the material being wound on reel 30.

The curvature of metering valve 48 may be so chosen that for ea-ch position thereof, which corresponds to a given pressure or torque at the motor 28, the size of opening, or the volume of fluid to the motor, is such that the product of motor pressure and volume is a constant. This relationship will produce constant tension on the strip material, neglecting losses at the reel and motor. Obviously, the curvature chosen may depart from this relationship as desired, either to compensate for such losses or to produce any predetermined variation in strip tension as the reel diameter increases.

At the completion of the winding operation, the control handle of valve 32 is shifted to connect conduit 38 with conduit 40 and to block conduits 34 and 36, thereby bypassing the fluid from pump I0 to tank I6, completely unloading pump I0 and thus stopping motor 28.

If a maximum .predetermined pressure is reached in the system, said maximum pressure being determined by the setting of spring 92 of valve 88, the resistance of spring 82 is overcome, valve 90 is unseated, and a pressure drop occurs in chamber 14 of valve 62 due to ow through restriction 82. This causes valve 68 to raise and exhaust the full delivery from pump |0 to tank I6 by means of seat 10, exhaust chamber 98, exhaust port 26 and conduit |00. When valve 80 opens, a pressure drop occurs in chamber 14 of valve 62 because fluid is able to escape from valve 88 by means of conduit 96, exhaust chamber 98, exhaust port 26 and conduit |00 to tank I6 faster than it can enter chamber 14 by way of conduit 80, restriction 82, control port 28 and passage 84 because of restriction 82. Overflow valve 62 is thereby raised by pressure acting on the lower face of piston 64 and thus performs the additional function of a, pressure responsive relief valve.

It should be noted that valve 42 may be originally adjusted by adjustable screw |04 to originally conduct an amount of fluid to motor 28 to create a maximum speed of the motor at the start of a winding operation commensurate With the diameter of reel 30. It should also be noted that, with an increase of pressure at motor 28, throttle 42 closes with an increase of such pressure to decrease the amount of fluid going to motor 28 and thereby decreasing its speed.

It should also be noted that valve 62 performs the double function of maintaining a constant pressure drop across throttle 42 for any given setting of such throttle and, in conjunction with valve 88, acting'as a system relief valve to limit maximum pump pressure.

In addition, pump lll does not operate continuously at the predetermined maximum pressure determined by spring 82 but only will exceed by a very small amount the pressure required to overcome the resistance offered by the gradually increasing diameter of the strip of material being wound on reel 30.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow. Although the invention has been shown to be suitable and adaptable for use in a hydraulic transmission for driving a reel comprising a fluid pump and motor driving the reel, it may be successfully applied in a similar hydraulic transmission for driving any load device where similar results are desired. Thus, the invention may be applied in a hydraulic transmission containing a uid pump and motor driving a load device where it is desired to drive the load device at varying and progressive speeds and torques but at substantially constant horsepower, or where a desired relationship between the speed of the driven load device and torque of the same is required in spite of a continuously varying load resistance, or where the speed of the driven load device must change in a predetermined relationship in response to changes in torque,

Certain subject matter in common with the present invention is disclosed and claimed in a copending application of Warren Brown, Serial No. 569,826, filed December 26, 1944, titled Power transmission.

What is claimed is as follows:

1. In a hydraulic power transmission system for driving a load device at varying speeds and torques but at substantially constant horsepower and containing a. fluid pump and motor, the combination of a flow regulating device comprising an adjustable throttle responsive to pressure changes at the motor whereby the throttle varies in predetermined relationship in response to said pressure changes, a compensating bypass valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle whereby the speed of the motor is changed relative to changes in pressures at the motor, and adjustable means responsive to a predetermined pressure whereby the compensating by-pass valve also performs the function of a system relief valve.

2. In a hydraulic power transmission system for driving a. load device at speeds which are varied in response to changes in torque and containing a fluid pump and motor. the combination of a flow regulating device comprising an adjustable throttle responsive to pressure changes at the motor whereby the throttle varies in predetermined relationship in response t'o said pressure changes, a compensating by-pass valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across thethrottle whereby the speed of the motor is changed relative to changes in pressure at the motor, and adjustable means responsive to a predetermined pressure whereby the compensating by-pass valve also performs the function of a system relief valve.

3. In a hydraulic power transmission system for driving a reel and containing a fluid pump and motor, the combination of a flow regulating device comprising an adjustable throttle responsive to pressure changes at the motor whereby the throttle varies in predetermined relationship in response to said pressure changes, a compensating by-pass Valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle whereby the speed of the motor is changed relative to changes in pressure at the motor, and adjustable means responsive to a predetermined pressure whereby the compensating by-pass`valve also performs the function of a systemfelief valve.

4. In a hydraulic power transmission system for driving a load device at speeds which are varied in response to changes in torque and containing a fluid pump and motor, the combination of a flow regulating device comprising an adjustable throttle responsive to pressure changes at the motor whereby the throttle tends to vary in predetermined relationship in response to said pressure changes, a compensating by-pass valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle whereby the speed of the motor varies relative to changes in pressure at the motor, and adjustable means responsive to a predetermined pressure whereby the compensating by-pass valve also performs the function of a system relief valve.

5. In a hydraulic power transmission system for driving a load device at speeds which are varied in response to changes in torque and containing a fluid pump and motor, the combination of a ow regulating device comprising an adjustable throttle responsive to pressure changes at the motor whereby the throttle tends to close in predetermined relationship in response to an increase of pressure at the motor, a compensating by-pass valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle whereby the speed of the motor decreases in predetermined relationship to pressure increases at the motor, and adjustable means responsive to a predetermined pressure whereby the compensating bypass valve also performs the function of a system relief valve.

6. In a hydraulic power transmission system for driving a load device atspeeds which are varied in response to changes in torque and containing a fluid pump and motor, the combination of a flow regulating device comprising a housing having an inlet port connected to the pump, an outlet port connected to the motor, a control port also connected to the motor, and an exhaust port and containing an adjustable, resilientlyloaded throttle in series with the pump and motor responsive to and adjustable by the pressure at the control port whereby the throttle tends to close in predetermined relationship to an increase of pressure at said motor, a compensating by-pass valve responsive to pressure changes ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle, and adjustable means cooperating with the compensating by-pass valve responsive to a predetermined pressure whereby the compensating 'oy-pass valve also performs the function of a system relief valve.

'7. A flow regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a passage through which fluid is adapted to flow at a regulated rate, a throttle in said passage, means for adjusting said throttle automatically in response to pressure changes at the outlet to said passage to regulate the throttle opening as a function of such pressure, a compensating bypass valve for maintaining a predetermined constant pressure drop across the throttle, and means whereby the compensating by-pass valve also performs the function of a pressure relief valve.

8. A flow regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a passage through which fluid is adapted to flow at a regulated rate, a throttle in said passage, means for adjusting said throttle automatically in response to pressure increases at the outlet to said passage whereby the throttle tends to close as a function of such pressure, a compensating bypass valve for maintaining a predetermined constant pressure drop across the throttle, and means whereby the compensating by-pass valve also performs the function of a pressure relief valve.

9. A flow regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a first passage through which fluid is adapted to ow at a regulated rate, an adjustable throttle in said first passage automatically responsive to pressure changes at the outlet to the first passage whereby the throttle resistance tends to vary as a function of such pressure, and a bypass passage in communication with the first passage, the outlet to which is controlled by a compensating bypass valve automatically responsive to pressure changes ahead of and beyond the throttle and designed to bypass a sufficient amount of fluid around the throttle to establish a predetermined relationship between the fluid flow through and the pressure at the outlet to the first passage.

10. A now regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a first passage through which fluid is adapted to flow at a regulated rate, an adjustable throttle in said first passage automatically responsive to pressure increases at the outlet to the first passage whereby the throttle resistance tends to close as a function of such pressure increases, and a bypasspassage in communication with the first passage, the outlet to which is controlled by a compensating bypass valve automatically responsive to pressure changes ahead of and beyond the throttle and designed to bypass a sufficient amount of fluid around the throttle to establish a predetermined relationship between the fluid flow through and the pressure at the outlet to the first passage.

11. A flow regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a first passage through which fluid is adapted to flow at a regulated rate, an adjustable throttle in said first passage automatically responsive to pressure increases at the outlet to the first passage whereby the throttle resistance tends to close as a function of such pressure increases, and a bypass passage in communication with the first passage, the outlet to which is controlled by a compensating bypass valve automatically responsive to pressure changes ahead of and beyond the throttle and designed to bypass a suicient amount of fluid around the throttle to maintain a substantially constant pressure drop across the throttle and to establish a predetermined relationship between the fluid flow through and the pressure at the outlet to the first passage.

12. A regulating device for use in a hydraulic power system for driving a load device at speeds which are varied in response to changes in torque and comprising in combination a first passage through which uid is adapted to fiow at a regulated rate, an adjustable throttle in said rst passage automatically responsive to pressure in creases at the outlet to the rst passage whereby the throttle resistance tends to close as a function of such pressure increases, a bypass passage in communication with the rst passage, the outlet to which is controlled by a compensating bypass valve automatically responsive to pressure changes ahead of and beyond the throttle and designed to bypass a sufilcient amount of fluid around the throttle to maintain a substantially constant pressure drop across the throttle and to establish a predetermined relationship between the uid ow through and the pressure at the outlet to the first passage, and means whereby the compensating bypass valve also performs the function of a pressure relief valve.

13. In a hydraulic power transmission for driving a load device at speeds which are varied in response to changes in torque and having a fluid pump and motor, the combination of a flow regulating device comprising an adjustable throttle automatically responsive to pressure increases at the motor whereby the throttle tends to close as a function of such increase of pressure, and a compensating bypass valve responsive to pressure changes ahead of and beyond the throttle and designed to bypass a sumcient amount of uid around said throttle to decrease the speed of the motor relative to an increase of torque at said motor.

14. In a hydraulic power transmission for driving a load device at speeds which are varied in response to changes in torque and having a uid pump and motor, the combination of a flow regulating device comprising an adjustable throttle automatically responsive to pressure increases at the motor whereby the throttle tends to close as a function of such increase of pressure. and a compensating bypass valve responsive to pressure changes ahead of and beyond the throttle and designed to bypass a suilcient amount of iiuid around said throttle to maintain a substantially constant pressure drop across the throttle and to decrease the speed of the motor relative to an increase of torque at said motor.

15. In a hydraulic power transmission for driving a load device at speeds which are varied in response to changes in torque and having a fluid pump and motor, the combination of a iow regulating device comprising an adjustable throttle automatically responsive to pressure increases at the motor whereby the throttle tends to close as a function of such increase of pressure, a compensating bypass valve responsive to pressure changes ahead of and beyond the throttle and designed to bypass a sufficient amount of fluid around said throttle to maintain a substantially constant pressure drop across the throttle and to decrease the speed of the motor relative to an increase of torque at said motor, and adjustable means cooperating with the compensating bypass valve responsive to a predetermined pressure whereby the compensating bypass valve also performs the function of a system relief valve.

JOSEPH J. GEORGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,082,473 Tyler June 1, 1937 2,164,599 Tyler July 4, 1939 2,255,783 Kendrick Sept. 16, 1941 

